Spirocyclisation of phytoalexin 1-methoxybrassinin in the presence of Grignard reagents

Abstract

AbstractThe anti-cancer properties of naturally occurring (2R, 3R)-(−)-1-methoxyspirobrassinol methyl ether (I) and their synthetic amino or piperidyl analogues II inspired us to study the synthesis of new target compounds III with a C—C bond in the 2-position of indole rather than a C—N or C—O bond (I or II respectively). The goal was achieved via electrophilic-nucleophilic 3,2-difunctionalisation of 1-methoxybrassinin (IV) in the presence of bromine and the Grignard reagent leading to the formation of cis- and trans-C—C analogues of I. Finally, the anti-cancer activities of the new compounds were measured and compared with I and II in order to show the importance of a heteroatom in the 2-substituted indole on the anti-cancer activity of spirobrassinols.